Zocdoc Answers

Medical questions & health advice by licensed doctors

"What are causes for occasional fatigue?"


My daughter is 19 years old and she says that she has a lot of fatigue recently. She does not exercise and she is not on any current medication. She enjoys to go out often with her friends. A few years ago she contracted mononucleosis. She goes to bed at about eleven or twelve o clock each night and she wakes up occasionally around seven if she has to work. She works as a medical assistant (filing papers and sometimes working at the front desk). What are the causes for her occasional fatigue?


The most common cause of fatigue is sleep deprivation. It sounds like you daughter may not be going to be early enough for a good night's sleep. If she goes to bed by midnight, she may not fall asleep till 12:30, then she'll get less than 7 hours of sleep.

See a doctor who can help

Find a Primary care-doctors near you

The first intervention I would undertake is seeing if she would be willing to go to bed earlier. Medical illnesses such as mononucleosis certainly cause a lot of fatigue while the infected person has an active infection. However, only a very small percentage of people experience fatigue years later. Other medical illness such as anemia can cause fatigue. Finally if your daughter is experiencing depression, this could be playing a role in her energy level and ability to get good sleep. I suggest that you schedule an appointment with your daughter's primary care physician. He or she can discuss you daughter's sleeping habits, her mood and any depression symptoms, and anything else that is going on. Her doctor will likely want to get some routine blood work such as a complete blood count to rule out anemia. Hopefully, she will feel better soon.

Zocdoc Answers is for general informational purposes only and is not a substitute for professional medical advice. If you think you may have a medical emergency, call your doctor (in the United States) 911 immediately. Always seek the advice of your doctor before starting or changing treatment. Medical professionals who provide responses to health-related questions are intended third party beneficiaries with certain rights under Zocdoc’s Terms of Service.